Apparatus for use in making reinforced edge apertures in heat shrinkable material



June 8, 1965 J. w. HARRISON 3,187,380

APPARATUS FOR USE IN MAKING REINFORCED EDGE APERTURES IN HEAT SHRINKABLEMATERIAL Original Filed March 21, 1961 2 Sheets-Sheet 1 IN VENTOR JOHNl# HARRISON ATTORNEYS June 8, 1965 J, w, HARRlsON 3,187,380

APPARATUS FOR UsE 1N MAKING REINFORCED EDGE APERTURES 1N HEAT SHRINKABLEMATERIAL Original Filed March 2l, 1961 2 Sheets-Sheet 2 Fla/0 F/G/f INVENT OR JOHN IY. HARRISON ATTORNEYS United States Patent O APPARATUS FORUSE IN MAKING REINFORCED' EDGE APERTURES IN HEAT SHRINKABLE MATERIAL fThis application is a'division of my copending application Serial No.97,307, led March 21, 1961, which issued as U.S. Patent No. 3,092,439 onJune 4, 1963. Application Serial No. 97,307 in turn is acontinuation-inpart of my application Serial No. 854,385, tiled November20, 1959, now abandoned.

The present invention relates to an apparatus for making a reinforcededge on an aperture in heat shrinkage material.

In the use of heat'shrinkable lm, especially in the packaging field, ithas been found necessary to provide holes or apertures, the holes orapertures serving various purposes. Heretofore, the apertures have beenmerely die cut or dinked in the ilm and such formed apertures have hadlimited usefulness due to the lilms low resistance to tear propagation.In other Words, such lapertures cannot stand much `stress as a tear canstart in their edges. Once a tear starts, it will propagaterapidlythrough the material.

An important object of the present invention is to provide an apparatusfor use in making a preliminary aperture in a heat shrinkable material,the aperture, when the material is heat shrunk, being so formed as todecrease the danger of tears starting from the edges of the apertures.

The present invention is particularly applicable to packages requiringapertures. A typical package would be one requiring a pour hole, a holefor the lifting ring of aA packaged electric motor. Another example ofthe us of a heat shrinkable material having apertures would be thepackaging of food products such as tea and colfee in bags. In eachinstance, it is highly desirable that the apertures inthe materialmaking up the package be provided with edges that are of a greater tearresistance than the lilm of the package.

`Another object of the present invention is to provide an apparatus forpreliminarily perforating a heat shrinkable material with an aperturehaving a thinned out or feathered edge so that when heat is applied inalocalized area about the preformed aperture, it causes the material toshrink back and form an aperture of desired size.

These and other objects and advantages of the present invention willappear more fully in the following specilication, claims and drawings inwhich:

FIGURE 1 is a fragmentary perspective view of a sheet of heat shrinkablematerial having a preformed aperture therein;

FIGURE 2 is a fragmentary perspective view of a sheet of heat shrinkablematerial, the preformed apertured having been formed toits nalconliguration; FIGURE 3 discloses a sectional view showing one method offorming the aperture in a `sheet of heat shrinkable material accordingto the present invention;

FIGURE 4 is a sectional view of the aperture formed ice FIGURE 7 is aschematic sectional view of an apparatus for preforming holes in a pieceof .heat shrinkable material according to the present invention;

FIGURE 8 is another schematic sectional view illustrating modifiedapparatus for forming a preformed hole in a piece of heat shrinkablematerial according to the present invention;

FIGURE 9 is an enlarged fragmentary cross-sectional view of theapparatus in FIGURE 8, the View further illustrating the feathered orthinned out edge on'the preformed aperture;

FIGURE 10 illustrates application of heat in a localized area to thepreformed aperture formed in accordanc with either FIGURES 7 or 8;

FIGURE 1l is a sectional View through'an aperture formed in accordancewith the present invention and illustrating its final configuration;

FIGURE 12 is a fragmentary top plan view of a preformed aperture justafter localized heat has been applied thereto showing the formation ofthe thickened ilexible edge.

Referring now to the drawings in which like character or referencenumerals represent like or similar parts, the present invention relatesto a method of providing an aperture in a film 10 of heat shrinkablematerial, the aperture being generally designated at 12 and having areinforced thickened flexible edge 14. As mentioned at the outset of thespecification, apertures have been provided in heat shrinkable materialby die cutting the hole but such apertures had limited usefulness astears would propagate from the edges of the aperture through the lrn orsheet of material. apertures have been made in nylon fabric used forwatch straps or the like by inserting a heated awl through the fabricwhich fuses the edges. However, this type of aperture is limited in itsusefulness since the edge is stiffened by the fusing of the nylon.

Preferably, the heat shrinkable material employed in the presentinvention is biaxially `oriented polyethylene having a shrink energy of250 p.s.i. at 96 C. The biaxially oriented polyethylene was prepared byirradiating Alathon 14 (polyethylene, molecular weight about 20,000,density 0.916) to a dosage of 12 megarad and then stretching 350% inboth directions.

There can be employed as the starting polyethylene for the irradiationprocedure high, low or medium density polyethylene prepared by low orhigh pressure techniques. The starting polyethylene can have a molecularWeight of 7,000 or 12,000 or 19,000 or 21,000 or 24,000 or 35,000 oreven higher.

In general, the polyethylene employed in the present invention is a lmor tubing which has been irradiated to an extent of 2te 100 megarad,preferably 6 to 20 megarad. The irradiation can be accomplished inconventional fashion, e.g., by -the use of a high voltage resonanttransformer, such as the 2,000,000 volt General Electric resonanttransformer, or high energy particle generators of 50,000 to 50,000,000volts, or a Van de Graaif electron generator. In addition tothe use ofelectrons, there can be employed beta rays, gamma rays, e.g., `byemploying cobalt 60, etc. There can be employed any of the irradiationprocedures disclosed in Baird application, Serial No. 713,848 ledFebruary 7, 1958, or Rainer Patent 2,877,500, for example. The entiredisclosure of the Baird application and the Rainer patent is herebyincorporated by reference. i

The biaxial orientation is normally carried Vout to an extent of 100 to700% longitudinally and 100 to 900% laterally. The biaxial stretchingcan be carried out by blowing irradiated polyethylene tubing asdisclosed in theA BairdV application; The 4irradiated biaxially'oriented Also, it might be mentioned thatV 3 polyethylene prepared bysuch a procedure has a high shrink energy, e.g., 100 to 500 p.s.i. at 96C.

In place of irradiated polyethylene, there can be employed similarlyirradiated polypropylene or polypropylene which has not been irradiated.

Referringkto FIGURES 1, 2 and 3, the aperature 12 in a film of biaxiallyoriented irradiated polyethylene can be formed with a thickened edgeportion 14 which is flexible and less oriented as well as having a hightear resistance by placing the sheet 10 with a preformed aperture 12' ona fiat surface 16. The preformed aperture 12 can be made by die cuttingthe hole and it is important that the aperture be free of any nicks orirregularities prior to the forming of the aperture of finalconfiguration. In FIGURE 1, the aperture is shown in circular form butit is, of course, within the scope of the invention that the aperturecan be any desired shape such as oval, rectangular or the like.

After the sheet 10 has been placed on the fiat surface 16 with thepreformed aperture 12' already cut therein, a thermally insulating mask17 having an aperture 18 of the same shape as the preformed aperture 12is placed over the film 10 so that the aperture 18 is concentric withthe aperture 12. The aperture 18 is substantially the same size as theaperture which is to be made in the film 10. Heat is then applied to thearea 20 of the film 10 which is uninsulated and the edges of theaperture 12 will shrink back and thicken so as to form the aperture 12with the 4thickened edge 14. The heat which is applied may be in theform of a radiant heat source, a blast of hot air, or the like. Theresultant edge 14 of the aperture 12 is thicker and less oriented thanthe film 10 and, consequently, the tear resistance of the edge 14 ismaterially increased.

Referring now to FIGURE 5, a modified method of forming the aperture 12in a film of biaxially oriented irradiated polyethylene is disclosed. Inthis instance, a sheet 10 of the polyethylene film is clamped betweenupper and lower plates 20 and 22, respectively. The plates 20 and 22 areprovided with mated apertures 24 and 26 having the desired shape andsubstantial size of the aperture to be formed in the film 10". Thepreformed aperture in this instance is made by a heated fid or blade 28centrally piercing the film 10 in the area of the apertures 24 and 26.Further, downward thrust of the fid or blade 28 causes the aperture madeby the initial piercing to shrink back and form the thickened flexiblering 14. In this instance, the heat is being applied by conduction fromthe fid or blade 28.

Referring now to FIGURE 6, a package utilizing the method of the presentinvention is disclosed. In more detail, the package is a container orbag 30 made of biaxially oriented irradiated polyethylene and providedwith a plurality of apertures 32 therein. The bag 30 may be providedwith a string handle 34 which is anchored in a heat seal 36. It will beunderstood that the bag, which is adapted to receive a food product atleast partially soluble in a liquid such as tea, coffee or the like, maytake other shapes and may be formed from sheet or tubular heatshrinkable polyethylene lm or the like.

By providing a bag of heat shrinkable material having apertures in itswalls, a new and novel package results. The bag 30 filled with the foodproduct may be inserted, for example, into a cup of hot water and thewater can flow through the apertures 32 and saturate the food product.Also, the heat of the water will cause the bag to shrink as its contentsare being dissolved, the shrinkage causing the tiavor to be expressedfrom thefood product through the apertures into the cup.

Referring now to FIGURES 7 through 14 inclusive, another means offorming an aperture in a film of heat shrinkable material isillustrated. .The film is biaxially oriented heat shrinkable material ofa polymer of an olefin having two to three carbon atoms as previouslydescribed. In this form of the invention, a preformed aperture is madein the film, the preformed aperture having a thinned out or featherededge. Heat is then applied to a localized area about the aperturecausing the film to shrink back and thicken and form an aperture ofincreased size having a thickened fiexible edge. By providing apreformed aperture in the film which has a thinned out or featherededge, the material of the thinned out feathered edge has both a highdegree of shrink and a high susceptibility to heat due to its low mass.Thus, as soon as heat is applied the film in the area of the featherededge, the edge begins to shrink back and thicken and any imperfection inthe edge will not propagate as the strain in the material has beenreduced because of the thickness of the edge in relation to theremaining portion of the film.

Referring now specifically to FIGURE 7, a machine for making a preformedhole or aperture in the film 40 is illustrated .and comprises a roller42 having hobnails or rounded projections 44 suitably spaced on itsperipheral surface. Cooperating with the roller 42 is a smooth surfacedroller 46, the smooth surfaced roller 46 rotating at the same surfacespeed as the roller 42. The film 40 is fed between the nip of therollers 42 and 46 and the hobnails or rounded projections 44 engagingthe film and causing it to fiatten out, a small hole being formedtherein and the film adjacent the hole a thinned out or feathered edge.The apparatus shown in FIGURE 7 would provide a hole in the film 40 bypressure of the hobnails or rounded projections 44 on the film againstthe roller 46 which in this case would be acting as an anvil.

Referring to FIGURES 8 and 9, still another form of apparatus is shownfor providing the preformed holes or apertures in the film 40, theapertures having a thinned out or feathered edge. The apparatus ofFIGURES 8 and 9 includes a roller 48 provided with hobnails or roundedprojections 50 on its peripheral surface and a coacting cylindrical`roller 52 having a plurality of tapered holes 54 in its outer peripherycooperating with the hobnails or projections 50. The interior of thecylinder 52 is connected with a suitable source of vacuum for removingthe center portion of the hole cut from the film 40 as shown in FIGURE9. Roller 48 and cylinder 52 rotate at the same surface speed so thatthe holes 54 in the cylinder 52 mate with the hobnails or projections 50of the roller 48 as the film 40 passes therebetween. In order thatvacuum will not be lost through the holes 54 when they are in a positionother than the position for preforming an aperture in the film, thecylinder 52 may be provided with a stationary internal shield 56 tocover the holes S4 except when the holes are actually mating with thehobnails or projections 50. As shown in FIG- URES 8 and 9, thestationary shield 56 is provided with an opening 58 at a point where thehole 54 mates with the hobnail or projection 50 of roller 48.

As shown in FIGURE 9, as the film passes between the roller 48 and thecylindrical roller S2, the pressure of the hobnail or projection S0 onthe film 40 causes a center section 60 to be punched from the film, thecenter section being drawn through the hole 54 into the center of theroller 52 by the vacuum. The inwardly tapered edge of the hole 54cooperating with the curved surface of the hobnail or projection 50thins out the edge of the preformed hole in film 40 so that the edge isrelatively feathered as shown at the right hand side of the figure. Byutilizing the apparatus of FIGURES 8 and 9, a slightly larger preformedhole can be provided in the film 40 than by the apparatus of FIGURE 7where pressure alone is utilized to cause a very small hole.

FIGURE 11 illustrates the application of heat by a suitable heating unit62 to the film 40 in the area of the preformed hole. Since the edge ofthe hole is feathered, the high shrink energy of the thin film in thisarea causes it immediately to shrink back and thicken, as shown inFIGURE lf).

Continued application of the heat will result in the aperture enlargingto the configuration shown in FIG- URE l1. The bead or edge 64 issubstantially thicke than the thickness of the film 40 and, of course,it will be less oriented, yet retain its flexibility and have a highertear resistance than the material of the film 40. While the heating unit62 is shown applying heat to a localized area, it is, of course, withinthe scope of the invention to utilize insulating means such aspreviously described in the specification to prevent the heat fromspreading to areas of the film other than the area immediately adjacentthe preformed hole.

It is also possible to take the film 40 with apertures therein andcompletely wrap an article and seal the package and then apply heat tothe wrapped package toshrink the film tightly around the package andsimultaneously to thicken the film around the periphery of the aperture.

In accomplishing the desired results that are set forth in the objectsand advantages of the present invention, and as described in detail inthe foregoing description, it will be perceived and obvious that theinvention is susceptible to some changes and modifications, both as tothe apparatus and resulting article, without departing from theprinciple .and spirit thereof. For this reason, the terminology used inthe specification is for the purpose of description and not oflimitation, the scope of the invention being defined in the claims.

I claim:

1, An apparatus for forming hole in a film of heat shrinkable materialcomprising: at least a pair of rotatable rollers arranged to rotate onparallel axes, one of said rollers having a rounded uninterrupted convexprojection on its peripheral surface physically engaging the other ofsaid rollers at the nip of said rollers whereby suicient pressure isapplied to the film by the rounded uninterrupted convex projection asthe film passes between the nip of the rollers to form an aperture inthe film with the edge portion of the film about the aperture beingthinned, the other of said rollers being provided with a hole inits'surface having a periphery engageable by mating with said roundeduninterrupted convex projection and through which the center portion ofthe material when the aperture is formed therein is received, andwherein an edge portion about the hole in the other of said rollers isconcaved inwardly and complementary to the rounded uninterrupted convexprojection of the one Vroller whereby the edge portion of the film aboutthe formed aperture is thinned to a feathered edge.

2. An apparatus for forming an aperture in a film of heat shrinkablematerial comprising: a pair of rotatable mating rollers, one of saidrollers having a rounded uninterrupted convex projection on itsperiphery, the other of said rollers being cylindrical and having itsinterior vacuumized, the other of said rollers also having a hole in itssurface, said hole having its periphery engageable by and mating withthe rounded uninterrupted convex projection on said one roller wherebysuliicient pressure is applied to the film by the rounded uninterruptedconvex projection to form an aperture in a film passing through the nipof said rollers, the portion punched out of the lm being withdrawnthrough the hole in the cylindrical roller, and wherein the cylindricalroller has an edge por-V rotatable rollers arranged to rotate onparallel axes, one

of said rollers having a rounded uninterrupted convex projection on itsperipheral surface, the other of said rollers having a hole in itssurface for cooperation with the said rounded uninterrupted convexprojection, means to form a feathered edge, said means being disposedabout the edge portion of the hole in the other of said rollers and saidmeans physically engaging said rounded uninterrupted convex projectionwith sufficient pressure sol that when the film passes therebetween, anaperture is formed in the'film with the edge portion of the film aboutthe aperture being thinned to a feathered edge.

4. An apparatus for forming an aperture in a film of heat shrinkablematerial comprising: at least a pair of rotatable mating rollers, one ofsaid rollers having a rounded uninterrupted convex projection on itsperiphery, the other of said rollers being cylindrical and having a holein its surface, said hole having its periphery engageable by and matingwith the rounded uninterrupted convex projection on said one roller,means to form a feathered edge, said means being disposed aboutr theedge portion of the hole in said other roller, said means physicallyengaging said rounded uninterrupted convex projection with sufficientpressure so that when the film passes therebetween, an aperture isformed in the film with the edge portion of the film about the aperturebeing thinned to a feathered edge, and vacuum means to withdraw theportion punched out of the vfilm through the hole in said Y otherroller.

References Cited by the Examiner UNITED STATES PATENTS 1,497,980 6/ 24Johnston.

1,750,708 3 30 Edwards.

1,890,424 12/ 32 Whitworth.

2,068,456 1/ 37 Hooper.

2,497,212 2/ 5 0 Donofrio 18--21 X 2,662,246 12/53 Klugh et al 18 -21WILLIAM J. STEPHENSON, Primary Examiner.

1. AN APPARATUS FOR FORMING HOLE IN A FILM OF HEAT SHRINKABLE MATERIALCOMPRISING: AT LEAST A PAIR OF ROTATABLE ROLLERS ARRANGED TO ROTATE ONPARALLEL AXES, ONE OF SAID ROLLERS HAVING A ROUNDED INTERRUPTED CONVEXPROJECTION ON ITS PERIPHERAL SURFACE PHYSICALLY ENGAGING THE OTHER OFSAID ROLLERS AT THE NIP OF SAID ROLLERS WHEREBY SUFFICIENT PRESSURE ISAPPLIED TO THE FILM BY THE ROUNDED UNINTERRUPTED CONVEX PROJECTION ASTHE FILM PASSES BETWEEN THE NIP OF THE ROLLERS TO FORM AN APERTURE INTHE FILM WITH THE EDGE PORTION OF THE FILM ABOUT THE APERTURE BEINGTHINNED, THE OTHER OF SAID ROLLERS BEING PROVIDED WITH A HOLE IN ITSSURFACE HAVING A PERIPHERY ENGAGEABLE BY MATING WITH SAID ROUNDEDUNINTERRUPTED CONVEX PROJECTION AND THROUGH WHICH THE CENTER PORTION OFTHE MATERIAL WHEN THE APERTURE IS FORMED THEREIN IS RECEIVED, ANDWHEREIN AN EDGE PORTION ABOUT THE HOLE IN THE OTHER OF SAID ROLLERS ISCONCAVED INWARDLY AND COMPLEMENTARY TO THE ROUNDED UNINTERRUPTED CONVEXPROJECTION OF THE ONE ROLLER WHEREBY THE EDGE PORTION OF THE FILM ABOUTTHE FORMED APERTURE IS THINNED TO A FEATHERED EDGE.